score=eval(input('请输入您的成绩:'))

if score<0 or score>=100:
    print('成绩有误')
elif 0 <= score < 60:
    print('E')
elif 60 <= score < 70:
    print('D')
elif 70 <= score < 80:
    print('C')
elif 80 <= score < 90:
    print('B')
else:
    print('A')